Method and system for analysis of bone density

ABSTRACT

The present invention relates to a method for generating a bone density value. The method comprises the steps of:
         generating digital image data depending upon an X-ray image corresponding to at least a part of the bone;   transmitting a digital image data signal comprising the digital image data; and   processing said digital image data signal. The processing step comprises the sub steps of:   generating a trabeculae model depending upon said processed digital image data signal;   generating at least one geometrical figure depending upon the generated trabeculae model, wherein the generated geometrical figure is provided essentially within a space at least partly defined by centre lines of the generated trabeculae;   calculating the bone density value depending upon the at least one generated geometrical figure.

FIELD OF THE INVENTION

The invention relates in particular to a method for computerizedanalysis of bones. The present invention relates to a system forcomputerized analysis of bones. The present invention also relates to acomputer programme comprising a programme code for performing the methodsteps according to the invention when the computer programme is run on acomputer.

BACKGROUND OF THE INVENTION

Trabecular bone of for example mammals must withstand the loads thatarise during daily activities as well as those from trauma.Investigation of the mechanical properties of trabecular bone presents achallenge because of its high porosity and complex architecture, both ofwhich vary substantially between anatomic sites and across individuals.

Today Osteoporosis is one major cause of fragile fractures, which is agreat national decease in several countries. Each year great resourcesof public or private medical service are used for treatment of patientssuffering of bone fractures resulting from different forms of trauma. Ofcourse, a combination of undiscovered Osteoporosis and incautiousactivities may easier result in bone fractures than if a diagnosis ofOsteoporosis would have been made and communicated.

There exist various ways to measure and/or determine bone mass and bonedensity. A well known procedure is to measure the density of a bone inantebrachium by means of a Dual X-ray absorptiometry (DXA). However, inpractice, often a great percentage of the population in a country isvulnerable to Osteoporosis but is not subjected to regular medicalexaminations. Use of DXA is associated with bulky equipment and highcosts.

US 2002 196966 discloses an automated method, storage medium, and systemfor analyzing bone. Digital image data corresponding to an image of thebone are obtained. Next there is determined, based on the digitalimages, a measure of bone mineral density (BMD) and at least one of ameasure of bone geometry, a Minkowski dimension, and a trabecularorientation. The strength of the bone is estimated based upon themeasure of BMD and at least one of the measure of bone geometery, theMinkowski dimension, and the trabecular orientation.

A measure of normalized bone mineral density (BMD) corresponding to avolumetric bone mineral density of the bone is determined, and thestrength of the bone based is estimated based at least in part on thenormalized BMD. However, the method and system is associated with aheavy computational burden.

SUMMARY OF THE INVENTION

An object of the invention is to overcome the drawbacks of prior artmentioned above.

Another object of the invention is to provide a more cost effectivesystem and method for detecting an indication that a bone suffers fromOsteoporosis.

Yet another object of the invention is to provide a method and systemwhich allows detecting an indication of that a bone suffers fromOsteoporosis in a fast, accurate and automated way, while reducing thecomputational complexity associated therewith.

Yet another object of the invention is to provide an improved procedureof computerized analysis of a bone, such as a jaw bone of a mammal.

Yet another object of the invention is to provide a computer programmefor improved computerized analysis of a bone, such as a jaw bone of amammal.

Yet another object of the invention is to provide a method and systemfor generating a value indicative of bone density for a bone having atleast one trabeculae.

According to an aspect of the invention there is provided a method forgenerating a value indicative of bone density for a bone having at leastone trabeculae; said method comprising the steps of:

-   -   generating a set of digital image data pixels depending upon an        X-ray image corresponding to at least a part of said bone;    -   classifying pixels selected from said set of digital image data        pixels according to predefined classification rules so as to        distinguish between trabeculae tissue and non-trabeculae tissue;    -   processing said classified pixels so as to generate at least one        trabeculae image; said at least one trabeculae image        corresponding to said at least one trabeculae;    -   generating at least one centre line associated with said at        least one trabeculae image; each said centre line being        indicative of a geometrical shape of said trabeculae image; and    -   generating a plurality of geometrical figures; each said        geometrical figure having a geometrical figure boundary defined        by said centre lines; said geometrical figure boundary being        selected so that the area of said geometrical figure represents        an area of non-trabeculae tissue located between said        trabeculae.

According to an aspect of the invention the problems described above canbe solved by a method for generating a bone density value comprising thesteps of:

-   -   generating digital image data depending upon an X-ray image        corresponding to at least a part of the bone;    -   transmitting a digital image data signal comprising the digital        image data;    -   processing said digital image data signal;        wherein        said processing step comprises the sub steps of:    -   generating a trabeculae model depending upon said processed        digital image data signal;    -   generating at least one geometrical figure depending upon the        generated trabeculae model, wherein the generated geometrical        figure is provided essentially within a space at least partly        defined by centre lines of the generated trabeculae;    -   calculating the bone density value depending upon the at least        one generated geometrical figure.

The method provides a low cost examination of Osteoporosis presence of amammal. This means that a relatively early detection of Osteoporosis canbe achieved.

Advantageously there is achieved a reduced computational load associatedwith the automatic computerized analysis because of the fact that theinvention is directed to determine space between trabeculae instead ofperforming calculations relating to the actual bone structure.

According to an aspect of the invention there is provided a computerreadable medium having embodied thereon a computer program forprocessing by a computer comprising:

-   -   a first code segment for processing digital image data, which        data is generated depending upon an X-ray image corresponding to        at least a part of a bone;    -   a second code segment for generating a trabeculae model        depending upon said processed digital image data;    -   a third code segment for generating at least one geometrical        figure depending upon the generated trabeculae model, wherein        the generated geometrical figure is provided essentially within        a space at least partly defined by centre lines of the generated        trabeculae; and    -   a fourth code segment for calculating bone density value of the        bone depending upon the at least one generated geometrical        figure.

Preferably the medium is a propagated signal.

Preferably the propagated signal is a carrier wave.

According to an aspect of the invention there is provided an apparatusfor generating a value indicative of bone density for a bone having atleast one trabeculae; said apparatus comprising:

-   -   means for generating a set of digital image data pixels        depending upon an X-ray image corresponding to at least a part        of said bone;    -   means for classifying pixels selected from said set of digital        image data pixels according to predefined classification rules        so as to distinguish between trabeculae tissue and        non-trabeculae tissue;    -   means for processing said classified pixels so as to generate at        least one trabeculae image; said at least one trabeculae image        corresponding to said at least one trabeculae;    -   means for generating at least one centre line associated with        said at least one trabeculae image; each said centre line being        indicative of a geometrical shape of said trabeculae image; and    -   means for generating a plurality of geometrical figures; each        said geometrical figure having a geometrical figure boundary        defined by said centre lines; said geometrical figure boundary        being selected so that the area of said geometrical figure        represents an area of non-trabeculae tissue located between said        trabeculae.

According to an aspect of the invention there is provided a system forgenerating a value indicative of bone density for a bone having at leastone trabeculae; said apparatus comprising:

-   -   means for generating a set of digital image data pixels        depending upon an X-ray image corresponding to at least a part        of said bone;    -   means for classifying pixels selected from said set of digital        image data pixels according to predefined classification rules        so as to distinguish between trabeculae tissue and        non-trabeculae tissue;    -   means for processing said classified pixels so as to generate at        least one trabeculae image; said at least one trabeculae image        corresponding to said at least one trabeculae;    -   means for generating at least one centre line associated with        said at least one trabeculae image; each said centre line being        indicative of a geometrical shape of said trabeculae image; and    -   means for generating a plurality of geometrical figures; each        said geometrical figure having a geometrical figure boundary        defined by said centre lines; said geometrical figure boundary        being selected so that the area of said geometrical figure        represents an area of non-trabeculae tissue located between said        trabeculae.

According to an aspect of the invention there is provided an apparatusfor generating a bone density value, comprising:

receiving means for receiving a digital image data signal comprisingdigital image data generated depending upon an X-ray image correspondingto at least a part of the bone;

processing means arranged to generate a trabeculae model depending uponsaid processed digital image data signal; wherein the processing meansfurther is arranged to generate at least one geometrical figuredepending upon the generated trabeculae model, wherein the generatedgeometrical figure is provided essentially within a space at leastpartly defined by centre lines of the generated trabeculae; and whichprocessing means further is arranged to calculate the bone density valuedepending upon the at least one generated geometrical figure.

Preferably the apparatus further comprising:

means for generating a plurality of geometrical figures.

Preferably the apparatus further comprising:

means for selecting the at least one geometrical figure to be a circle.

Preferably the apparatus further comprising:

means for providing the at least one geometrical figure in a spacerelating to regions provided essentially between the generatedtrabeculae.

Preferably the apparatus further comprising:

means for manually selecting a region of interest depending upon saidX-ray image, wherein at least a part of said bone is provided withinsaid region of interest; and/or means for automatically selecting aregion of interest depending upon said X-ray image, wherein at least apart of said bone is provided within said region of interest.

Preferably the apparatus further comprising:

means for normalizing said digital image data.

Preferably the apparatus further comprising:

means for generating set up information comprising information aboutimage brightness and/or radiation dose information; and

means for including the set up information in the digital image datasignal.

An aspect of the invention relates to a system comprising imagegenerating means for generating digital image data depending upon anX-ray image corresponding to at least a part of the bone;

means for transmitting a digital image data signal comprising thedigital image data; and

an apparatus as defined above.

According to an aspect of the invention there is provided a computerprogram product comprising a computer readable medium having embodiedthereon a computer program for processing by a computer, said computerprogram comprising:

-   -   a first code segment for generating a set of digital image data        pixels depending upon an X-ray image corresponding to at least a        part of said bone;    -   a second code segment for classifying pixels selected from said        set of digital image data pixels according to predefined        classification rules so as to distinguish between trabeculae        tissue and non-trabeculae tissue;    -   a third code segment for processing said classified pixels so as        to generate at least one trabeculae image; said at least one        trabeculae image corresponding to said at least one trabeculae;    -   a fourth code segment for generating at least one centre line        associated with said at least one trabeculae image; each said        centre line being indicative of a geometrical shape of said        trabeculae image; and    -   a fifth code segment for generating a plurality of geometrical        figures; each said geometrical figure having a geometrical        figure boundary defined by said centre lines; said geometrical        figure boundary being selected so that the area of said        geometrical figure represents an area of non-trabeculae tissue        located between said trabeculae.

Preferably the medium is a propagated signal.

Preferably said propagated signal is a carrier wave.

Additional objects, advantages and novel features of the presentinvention will become apparent to those skilled in the art from thefollowing details, as well as by practice of the invention. While theinvention is described below, it should be understood that the inventionis not limited to the specific details disclosed. A person skilled inthe art having access to the teachings herein will recognise additionalapplications, modifications and embodiments in other fields, which arewithin the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and furtherobjects and advantages thereof, reference is now made to the examplesshown in the accompanying drawings, in which:

FIG. 1 schematically illustrates an overview of a system for generatingbone information according to an aspect of the invention.

FIG. 2 schematically illustrates an arrangement according to an aspectof the present invention.

FIG. 3 a schematically illustrates a method for generating boneinformation according to an aspect of the invention.

FIG. 3 b schematically illustrates a method for generating boneinformation in greater detail according to an aspect of the invention.

FIG. 3 c schematically illustrates a method for generating boneinformation in greater detail according to an aspect of the invention.

FIG. 4 schematically illustrates a representation of an X-ray image.

FIG. 5 a schematically illustrates a set of trabeculae generated by askeletonization process.

FIG. 5 b schematically illustrates the set of trabeculae provided withcentre lines.

FIG. 5 c schematically illustrates the set of trabeculae provided withgeometrical figures.

DETAILED DESCRIPTION OF DRAWINGS

FIG. 1 schematically illustrates a system 10 according to an aspect ofthe invention. The system 10 is arranged to perform a computerizedanalysis of an object, such as a bone of a mammal. The system 10 isarranged for generating a piece of information comprising informationabout the object.

The object is referred to as object 5. According to the preferredembodiment of present invention the object is a human being. Morespecific, a preferred region of interest (ROI) is a mandible, i.e. alower jaw, of a living person, such as a patient at a dentist's office.Alternatively, the object may be a bone of a dead animal to beinvestigated.

The system 10 comprises an image generating means 110, which is arrangedfor communication with an image processing means 100 via a link 181. Animage providing means 120 is arranged for communication with the imageprocessing means via a link 182. An input/output unit 130 is arrangedfor communication with the image processing means 100 via a link 183.The image generating means 110 and the image providing means 120 mayalso be arranged for communication with a communications network 140,such as a WAN, local network or Internet, via links 185 and 184,respectively. The communication network is further arranged forcommunication with the image processing means via a link 186.

The image generating means 110 is according to a preferred embodiment anX-ray system comprising a radiating unit 111 and a detector unit 112.The X-ray system may be of arbitrary size. The X-ray system ispreferably arranged for radiating a person's jaw region, such as beingperformed at a dentist's office or at a hospital. The system is arrangedto generate digital image data D1 corresponding to an image of a bone,for example the lower jaw bone of a person. The image generating means110 is arranged to generate a plurality of digital image data D1-DN,where N is a positive integer.

The image generating means 110 is arranged to generate and transmit thedigital image data D1-DN to the image processing means 100 via a link181 in form of digital image data signals S1-SN, respectively. The imagegenerating means 110 is also arranged to generate image characteristicinformation C1-CN, respectively, associated with each digital image dataD1-DN. The image generating means 110 is arranged to incorporate imagecharacteristic information to a corresponding image data signal S1-SN.Thus, the image data signal S1 comprises image characteristicinformation C1, the image data signal S2 comprises image characteristicinformation C2 etc.

According to an embodiment of the invention the generated image datasignals S1-SN are transmitted via the network 140. This embodiment issuitable if the image generating means 110 is provided in a distancedrelationship regarding the image processing means 100, for example ifimage processing is to be performed in a different city from where theimages were generated.

According to an alternative embodiment X-ray photographs (non digital)may be transformed to digital form. This can be performed by using asuitable image providing means 120, such as a scanner. The imageproviding means 120 is arranged to transmit digital image data signalsS1-SN, according to what is depicted with reference to the imagegenerating means 110, and transit the signals to the image processingmeans 100. The image data signals S1-SN may be transmitted either viathe link 182 or via the network 140, as depicted above.

The input/output unit 130 may comprise a monitor, PDA, microphone,loudspeaker, PC, or other. The input/output unit 130 may also comprise auser interface for an operator (e.g. a dentist or a medicine doctor).The input/output unit 130 is arranged to communicate a result of thecomputerized analysis of the object. For example by providing arepresentative numeric value on a screen, or by play back a voicemessage indicating said representative numeric value. Said value mayindicate a bone hardness value, such as a bone/non-bone ratio regardingthe region of interest of the object 5.

The input/output unit 130 is arranged is arranged to allow an operatorto manually take part is the method according to the invention. Forexample, in the case of using a touch-screen as input/output unit 130,an operator may manually define the region of interest by indicating thesame on said screen. Alternatively, in the case of using a monitor of aPC, the operator may manually define the region of interest byindicating the same on said monitor by means of a cursor and a mouse.

It should be noted that the term “link” herein refers to both a wirelesslink, such as a Bluetooth or radio link, and a physical link, such as awire or fiber optic cable.

With reference to FIG. 2, a diagram of one embodiment of an apparatus200 is shown. The above-mentioned image processing means 100 may includethe apparatus 200. The apparatus 200 comprises a non-volatile memory220, a data processing device 210 and a read/write memory 250. Thenon-volatile memory 220 has a first memory portion 230 wherein acomputer program, such as an operating system, is stored for controllingthe function of the apparatus 200. Further, the apparatus 200 comprisesa bus controller, a serial communication port, I/O-means, anA/D-converter, a time date entry and transmission unit, an event counterand an interrupt controller (not shown). The non-volatile memory 220also has a second memory portion 240.

A computer program comprising routines for carrying out processing andanalysis of the image data signals S1-SN and further implementingpredetermined actions, such as generating an indication of presence ofOsteoporosis is provided. The program may be stored in an executablemanner or in a compressed state in a memory 260 and/or in read/writememory 250. At least one computer programme arranged to perform methodsteps according to FIG. 3 a-3 c is provided in either the memory 260and/or in read/write memory 250.

The data processing device 200 may be, for example, a microprocessor.

When it is described that the data processing device 210 performs acertain function it should be understood that the data processing device210 performs a certain part of the programs which are stored in thememory 260, or a certain part of the program which is stored in theread/write memory 250.

The data processing device 210 may communicate with a data port 290 bymeans of a data bus 215. The non-volatile memory 220 is adapted forcommunication with the data processing device 210 via a data bus 212.The separate memory 260 is adapted to communicate with the dataprocessing device 210 via data bus 211. The read/write memory 250 isadapted to communicate with the data processing device 210 via a databus 214.

When data, such as data provided in the signals S1-SN, is received onthe data port 290 it is temporarily stored in the second memory portion240. When the received input data has been temporarily stored, the dataprocessing device 210 is set up to perform execution of code in a mannerdescribed above. According to one embodiment, data received on the dataport 290 comprises information about at least one digital imagecorresponding to an object, wherein a region of interest (ROI) isselected. This information can be used by the apparatus 200 so as togenerate a accurate indication of to what extent, if at all, a personsuffers from Osteoporosis.

Parts of the methods described herein can be performed by the apparatus200 by means of the data processing device 210 running the programstored in the memory 260 or read/write memory 250. When the apparatus200 runs the program, parts of herein described methods are executed.

FIG. 3 a schematically illustrates a method for generating a bonehardness value according to an aspect of the invention.

The method comprises a method step S300 regarding a method forgenerating a bone density value.

The method step S300 comprising the sub steps of:

-   -   generating digital image data depending upon an X-ray image        corresponding to at least a part of the bone;    -   transmitting a digital image data signal comprising the digital        image data;    -   processing said digital image data signal;        wherein        said processing step comprises the sub steps of:    -   generating a trabeculae model depending upon said processed        digital image data signal;    -   generating at least one geometrical figure depending upon the        generated trabeculae model, wherein the generated geometrical        figure is provided essentially within a space at least partly        defined by centre lines of the generated trabeculae;    -   calculating the bone density value depending upon the at least        one generated geometrical figure.

Preferably the method further comprises the step of

-   -   generating a plurality of geometrical figures.

Preferably the method further comprises the step of:

-   -   selecting the at least one geometrical figure to be a circle.

Preferably the method further comprises the step of:

-   -   providing the at least one geometrical figure in a space        relating to regions provided essentially between the generated        trabeculae.

Preferably the method further comprises the step of:

-   -   manually selecting a region of interest depending upon said        X-ray image, wherein at least a part of said bone is provided        within said region of interest; or    -   automatically selecting a region of interest depending upon said        X-ray image, wherein at least a part of said bone is provided        within said region of interest.

Preferably the method further comprises the step of:

-   -   normalizing said digital image data.

Preferably the method further comprises the steps of:

-   -   generating set up information comprising information about image        brightness and/or radiation dose information; and    -   including the set up information in the digital image data        signal.

FIG. 3 b schematically illustrates a method for generating a bonehardness value in greater detail according to an aspect of theinvention.

The method comprises a first method step S310. The method step S310comprises a sub step of generating digital image data corresponding toat least one image of an object 5 based upon detected X-rays. Accordingto a preferred embodiment the generated X-ray image comprisesinformation relating to a jaw bone of a mammal, such as a human being.Next, a subsequent method step S315 is performed.

The method step S310 comprises a step of transmitting digital image data(D1-DN) relating to the at least one digital image as a correspondingsignal (S1-SN). Image set up parameters are also included. Typicalparameters are image resolution information and image radiation doseinformation. Next, a subsequent method step S320 is performed.

The method step S320 comprises a step of processing the received digitalimage signals S1-SN relating to the at least one digital image,respectively. This step is depicted in greater detail with reference toFIG. 3 c. Next, a subsequent method step S325 is performed.

The method step S320 comprises a step of generating a bone hardnessvalue depending upon said processing of the received digital imagesignals S1-SN relating to the at least one digital image, respectively.Next, a subsequent method step S330 is performed.

The method step S320 comprises a step of outputting the generated bonestructure strength value. The value can for example be displayed on amonitor or provided by means of a loudspeaker. Thereafter the methodends.

With reference to FIG. 3 c a part of a method for generating a bonehardness value is depicted in greater detail according to an embodimentof the invention.

The method comprises a first method step S335. The method step S335comprises a step of determining a region of interest (ROI) of least oneimage in digital form based upon detected X-rays. This method step couldbe performed manually or automatically as depicted with reference toFIG. 1. If the method step is performed automatically a manual check maybe arbitrary performed. Next, a subsequent method step S340 isperformed.

The method step S340 comprises a step of reducing noise of the at leastone image. This noise may be a result of different sources. For example,one noise source is the detector unit 112 arranged to receive X-rayspropagated through at least a part of the object 5, such as a lower jawbone of a person, within an X-ray apparatus 110. The noise reductionprocess may be performed by known methods, such as, median filtering orin combination with linear convolution based methods. Next, a subsequentmethod step S350 is to be performed.

The method step S350 comprises a step of adjusting brightness of the atleast one image. This step is performed using various known methodsbased on intensity histogram analysis. Next, a subsequent method stepS355 is to be performed.

The method step S355 comprises a step of re-sampling the digital imagedata of the signals S1-SN relating to the at least one digital image,respectively. According to an embodiment of the invention, adown-sampling of the data is performed providing a lower resolution ofthe images. Next, a subsequent method step S360 is to be performed.

It should be noted that the method steps depicted above with particularreference to S340, S350 and S355 relate to a procedure of normalizingthe digital image data corresponding to the at least one image. This mayof course be performed in various ways. However, for the sake of clarityonly these steps are depicted. A person skilled in the art would be ableto modify the depicted normalization process according to specificneeds. One purpose of normalizing the digital image data is to achieve aset of data having desired properties for further processing. Thenormalized set of digital image data relating to a specific generatedimage is comparable with other normalized digital image data relating toanother specific generated image, regarding for example image resolutionand radiation dose. It should however be noted that other set upparameters may be of relevance in a normalization process. Examples ofsuch parameters are exposure time, bit depth/intensity quantization,X-ray acquisition method.

The method step S360 comprises a step of transforming the normalizeddigital image intensity data to binary data form. According to an aspectof the invention the set of data is transformed to tertiary data.According to an aspect of the invention the set of data is transformedto an arbitrary degree of differentiation, for example a fourth or fifthdegree of differentiation. Next, a subsequent method step S365 is to beperformed.

Thus a classification process of normalized digital image data relatingto each pixel thereof is performed. This process may comprise the substeps of comparing digital image data associated with each pixel of theimage with digital image data associated with each adjacent pixel. Forexample, each pixel of the image could be compared with the eightclosest pixels regarding for example brightness. If the brightness of anadjacent pixel is larger that a predetermined threshold value the twopixels is classified as belonging to different components of the object,for example, jaw bone and gums.

When all pixels have been classified, regarding for example brightness,a filtering process is applied. This filtering process involvesdifferent aspects of changing classification of individual pixels of theimage as well as set of pixels. For example, if one pixel in a center ofa large group of pixels is deviating regarding its classification thispixel may be re-classified, in accordance with the surrounding pixels.The same principles may apply to a group of deviating pixels within aparticular area of the region of interest. There exist standard methodsfor performing a filtering process according to what is generallydepicted above. Examples of such mathematical morphology methods areopening, closing, thinning and pruning.

The method step S365 comprises a step of performing a skeletonizingprocess. Standard techniques are available on the market today. Inshort, skeletonization is basically a process for reducing foregroundregions in a binary image to a skeletal remnant that largely preservesthe extent and connectivity of the original region while reducing mostof the original foreground pixels.

Herein, one or more centre axes are generated and associated with eachgenerated trabeculae. This is depicted in greater detail with referenceto FIG. 5 b. Next, a subsequent method step S370 is to be performed.

The method step S370 comprises a step of performing a distancetransformation on the area between the skeletonized trabeculae. The stepof distance transformation is performed depending upon the generatedskeleton model with reference to the method step S365. One way toperform this step is to determine, for each pixel of the digital image,distances from a pixel to a closest pixel which is provided at a centreaxis, i.e. for each pixel of the image the shortest distance to askeleton pixel is determined.

According to a preferred embodiment circles are generated depending uponsaid distance transformation. However, an arbitrary geometrical figuremay be used, for example hexagons or heptagons. The number and the sizeof geometrical figures within the selected region of interest is ameasure of trabeculae density of the bone. This measure is an indicationof how many trabeculae there is provided within the region of interest.Studies have shown that this value, which according to a preferredembodiment is associated with a lower jaw bone of a person is indicativeof the number of trabeculae in a region located in a different bone ofthe person's body, for example an upper end (at a hip) of femur.

There is an advantage associated with this procedure because it is lessdepending upon faulty segmentation of the trabeculae.

Next, a method step S375 is performed. The method step S375 comprisesthe step of calculating a numerical value indicating how much spacethere is between the generated trabeculae. This calculation is performeddepending upon the number of generated geometric figures within theregion of interest. This calculation is performed depending upon thesize of the generated geometric figures. Preferably the geometricfigures are circles. In the case of the geometric figures are circles,their respective radius is taken into account in the calculation. Thecalculated numerical value may be an indication of bone density. Thecalculated numerical value is then outputted. Alternatively, a symbolrepresenting the numerical value is outputted.

An aspect of the invention relates to a computer programme comprising aprogramme code for performing the method steps according to theinvention, when the computer programme is run on a computer.

An aspect of the invention relates to a computer programme productcomprising a program code stored on computer-readable media forperforming the method steps according to the invention, when thecomputer programme is run on the computer.

An aspect of the invention relates to a computer programme productdirectly storable in an internal memory of a computer, comprising acomputer programme for performing the method steps according to theinvention, when the computer programme is run on the computer.

FIG. 4 schematically illustrates a simplified representation of a 2-Ddigital image generated depending upon detected X-rays transmittedthrough an object. According to a preferred embodiment the object is apart of a mammal or other type of animal comprising an internalskeleton. According to more preferred embodiment of the invention theobject is a part of a mammal, wherein said object comprises at least apart of a bone, preferably trabecular bone. According to a preferredembodiment the object is a part of a mammals head, such as a jaw bone.

The invention is advantageous because digital X-ray generated image datamay be produced in a situation where a patient is visiting a dentist. Itshould be noted that this typically generated digital image data is wellsuited for being processed according to the invention.

The digital image data indicates that the object which has beensubjected to X-rays by the image generating means is a part comprisingtwo teeth and a lower jaw bone. There is indicated that an automaticallyor manually selected region of interest A is located essentiallycovering a part of the jaw bone and to a small extent gums between thefirst and second tooth T1 and T2. The region of interest is alsoreferred to as ROI.

FIG. 5 a schematically illustrates a skeleton model regarding a selectedregion of interest A. This skeleton model comprises three separatedtrabeculae 510 a, 520 a and 530 a, respectively. It should be noted thatonly a 2-D model is depicted with reference to the FIGS. 5 a-5 c.

The trabeculae 510 a, 520 a and 530 a has been generated by means of askeletonizing procedure. The trabeculae 510 a is referred to as a firsttrabeculae 510 a. The trabeculae 520 a is referred to as a secondtrabeculae 520 a. The trabeculae 530 a is referred to as a thirdtrabeculae 530 a. The trabeculae 510 a, 520 a and 530 a thus representthree trabeculae which are automatically identified from the digitalimage data, for example D1.

FIG. 5 b schematically illustrates an example of generated centre lines.The first trabeculae 510 a is provided with a first centre axis 510 b.The second trabeculae 520 a is provided with four centre axes 520 b 1,520 b 2, 520 b 3 and 520 b 4, respectively. Depending upon the shape ofa particular trabeculae an arbitrary number of centre axes may begenerated. The third trabeculae 530 a is provided with a first centreaxis 530 b. Further, two pixel points P1 and P2 are illustrated.

FIG. 5 c schematically illustrates four generated example circles ofdifferent radius r1, r2, r3 and r4. As can be seen they are all fittedbetween the generated centre axes of the generated trabeculae. Thesecircles are automatically analysed so as to generate a bone densityvalue or a value indicating to what extent the bone of the objectsuffers from Osteoporosis.

The foregoing description of the preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated.

1. Method for generating a value indicative of bone density for a bonehaving at least one trabeculae; said method comprising: generating a setof digital image data pixels depending upon an X-ray image correspondingto at least a part of said bone; classifying pixels selected from saidset of digital image data pixels according to predefined classificationrules so as to distinguish between trabeculae tissue and non-trabeculaetissue; processing said classified pixels so as to generate at least onetrabeculae image; said at least one trabeculae image corresponding tosaid at least one trabeculae; generating at least one center lineassociated with said at least one trabeculae image; each said centerline being indicative of a geometrical shape of said trabeculae image;and generating a plurality of geometrical figures; each said geometricalfigure having a geometrical figure boundary defined by said centerlines; said geometrical figure boundary being selected so that the areaof said geometrical figure represents an area of non-trabeculae tissuelocated between said trabeculae.
 2. The method of claim 1, wherein saidbone comprises the jawbone of a mammal.
 3. The method of claim 1,wherein classifying comprises comparing digital image data associatedwith each pixel of the image with digital image data associated witheach adjacent pixel.
 4. The method of claim 1, further comprising afterclassifying, the step of filtering.
 5. The method of claim 4, whereinfiltering comprises one or more of changing a classification ofindividual images or changing a classification of a set of pixels. 6.The method of claim 4, wherein filtering comprises one or more ofopening, closing, thinning or pruning.
 7. The method of claim 1, whereinthe geometric figures comprise circles.
 8. The method of claim 1,further comprising, after generating a set of digital image data pixels,transmitting the set of digital image data pixels.
 9. The method ofclaim 8, wherein transmitting comprises transmitting via a network. 10.The method of claim 1, further comprising manually selecting a region ofinterest depending upon said X-ray image, wherein at least a part ofsaid bone is provided within said region of interest.
 11. The method ofclaim 1, further comprising automatically selecting a region of interestdepending upon said X-ray image, wherein at least a part of said bone isprovided within said region of interest.
 12. The method of claim 1,further comprising normalizing said digital image data.
 13. The methodof claim 1, further comprising generating set up information comprisinginformation about image brightness, radiation dose information or both.14. The method of claim 13, further comprising including the set upinformation in the digital image data.
 15. A method for generating avalue indicative of bone density for a bone including at least onetrabeculae, said method comprising: classifying pixels selected from aset of digital image data pixels of an image corresponding to at least apart of said bone according to predefined classification rules so as todistinguish between trabeculae tissue and non-trabeculae tissue;processing said classified pixels to generate at least one trabeculaeimage; said at least one trabeculae image corresponding to said at leastone trabeculae; generating at least one center line associated with saidat least one trabeculae image; said center line being indicative of ageometrical shape of said trabeculae image; and generating a pluralityof geometrical figures including a geometrical figure boundary definedby said center line; said geometrical figure boundary being selected sothat the area of said geometrical figure represents an area ofnon-trabeculae tissue located between said trabeculae.